Method and composition for enhancing the performance of an emulsion-based surface treatment

ABSTRACT

The invention is a method of treating, restoring or sealing a surface comprising applying an emulsion comprising a latex polymer, a cationic emulsifier, and optionally a recycling agent to the surface to wet the surface and depositing a surface treatment layer on the surface, wherein the depositing step occurs while the surface is wetted. The invention also includes a surface pretreatment composition comprising water, at least one acrylic latex polymer, an aromatic recycling agent, and at least one cationic emulsifier. Furthermore, the invention includes the surface resulting from the application of the emulsion used in the invention and concentrated emulsions for use with the surface treatment composition.

FIELD OF THE INVENTION

The present invention relates to polymer dispersions for pavingapplications and particularly compositions and methods for improving theperformance of cold paving applications such as microsurfacing andslurry seal applications.

BACKGROUND OF THE INVENTION

Asphalt concrete, also known as asphalt pavement, is a compositematerial comprising mineral aggregate and asphalt (bitumen) binder whichhardens to form a robust surface. Early in its life, the asphaltconcrete has the ability to resist erosion, compressive deformation, andload fracture. However, as the asphalt concrete ages, the asphaltoxidizes, decreasing the binding capacity, increasing the viscosity, andfurther hardening the asphalt concrete. This leads to cracks in theasphalt concrete surface. Small cracks in the surface of the asphaltconcrete allow for further water intrusion into the asphalt concrete,and the oxidized asphalt concrete is more susceptible to structuralweakening and failure due to the reduction in binding capability.

Several surface treatment methods for aged asphalt are known whichcomprise adding a thin layer of modified asphalt concrete to extend thestructural life of the asphalt concrete. Such surface treatment methodsinclude chip seal, slurry seal, and microsurfacing treatments. However,the known slurry seal and microsurfacing treatments do not themselvesform a water-tight layer. Without a water-tight layer, the older,underlying asphalt concrete continues to oxidize and crack therebycausing reflective cracks in the new surface layer. Furthermore, theslurry seal or microsurfacing layer does not adhere well to a highlyoxidized asphalt concrete surface.

To address this problem and provide a water barrier between the oldasphalt concrete and the new surface layer, a tack coat can be appliedto the old asphalt concrete prior to slurry seal or microsurfacingoperations. The tack coat typically comprises a cationic or anionicdiluted asphalt emulsion comprising asphalt, water, latex polymer,emulsifier, and an optional aromatic recycling agent. The tack coat isapplied to the old asphalt concrete surface and cured to form acontinuous film on the older asphalt concrete which is air andwater-tight. The film prevents further oxidation and water damage of theold asphalt concrete. If the tack coat includes a large amount ofpolymer latex, it can also reduce the penetration of cracks into the newsurface layer (reflective cracks) and improve the adhesion between theold asphalt concrete and the new layer. The optional aromatic recyclingagent can rejuvenate the older, oxidized asphalt concrete by restoringthe aromatic content of the oxidized asphalt.

Another way to prevent reflective crack formation in the new surfacelayer is to apply a chip seal to the older asphalt pavement prior toslurry seal or microsurfacing applications. The process of applying achip seal prior to slurry seal or microsurfacing is also known as capeseal, as it was first developed in Cape Town, South Africa. During thechip seal process, the asphalt pavement surface is first sprayed with anasphalt emulsion comprising asphalt, water, an emulsifier (typically acationic rapid set emulsifier), and optionally a polymer latex. Then,aggregate is spread onto the asphalt emulsion and the aggregate iscompacted with pneumatic tires. The chip seal surface then must be curedfor 5-10 hours. Before the surface can be opened to regular use, thechip seal surface must also be swept to remove loose aggregate,typically 3-5 hours after application of the asphalt emulsion andaggregate. Chip seal uses single sized aggregate which forms a surfacewith a plurality of air voids. The air voids act as termination pointsfor cracks from the older asphalt pavement thus preventing reflectivecrack formation in the new surface layer. After application and curingof the chip seal layer, the slurry seal or microsurfacing layer isapplied. The slurry seal or microsurfacing layer then provides atraction surface.

Both the tack coat layer and the chip seal layer described above must becured with sufficient strength to support traffic before the finalsurface treatment is applied. As a result, it takes a minimum of threehours for the tack coat layer or chip seal layer to be sufficientlycured such that the microsurfacing or slurry seal layer can be appliedand ultimately before the asphalt concrete surface can be subjected tonormal use. Moreover, with the above-described processes known in theart, two separate operations are required before an aged asphaltconcrete surface is sufficiently restored and ready for normal use. Thisresults in prolonged lane or road closure, which is undesirable.Furthermore, the need for two separate application steps with a curingstep in between adds to the cost of the treatment due to the cost ofusing two road crews and their equipment, in addition to the costsrelated to prolonged lane closure.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the problems of the prior art byproviding a method of restoring or treating a surface with a singlecuring operation. In one embodiment, the method of restoring or treatinga surface comprises applying an emulsion to wet the surface anddepositing a surface treatment layer on the surface while the surfaceremains wetted with the emulsion. The emulsion preferably compriseswater (typically 70% water by weight or greater), a latex polymer, anaromatic recycling agent, and an emulsifier. Preferably, the emulsifieris a cationic emulsifier. In one preferred embodiment, the aromaticrecycling agent is mixed with water and an emulsifier to produce aconcentrated emulsion of the aromatic recycling agent and theconcentrated emulsion is combined with the emulsifier, water, and thelatex polymer for use in the invention. The concentrated emulsion can becombined with the emulsifier, water, and the latex polymer, for example,by mixing the concentrated emulsion with a cationic emulsifier solutionto produce a diluted emulsion of the aromatic recycling agent and mixingthe diluted emulsion with a polymer latex emulsion to produce theemulsion for use in the invention. Alternatively, a concentratedemulsion including the aromatic recycling agent, polymer latex,emulsifier and water can be prepared and then diluted with water to beapplied to the surface. The surface is typically an asphalt concretesurface that has undergone some degree of oxidation of the asphalt;however, the surface can be other types of surfaces, such as cementconcrete, unoxidized asphalt concrete, or any other porous surface towhich a surface asphalt concrete layer can be applied. In preferredembodiments, the surface treatment layer is either a microsurfacinglayer or a slurry seal and can include gap graded aggregate.

The present invention also provides a method of sealing a porous surfacecomprising spraying the surface with an emulsion comprising water, alatex polymer, and a cationic emulsifier. The emulsion preferablyfurther includes an aromatic recycling agent.

The present invention further provides a surface pretreatmentcomposition comprising water, an acrylic latex polymer, an aromaticrecycling agent, and an emulsifier. The composition typically includesfrom 70% to 96% by weight water, from 2% to 15% by weight acrylic latexpolymer, from 2% to 15% by weight aromatic recycling agent; and fromgreater than 0% to 2% by weight emulsifier. Preferably, a cationicemulsifier is used and the acrylic latex polymer is compatible with thecationic emulsifier in that the latex particles remain as a stabledispersion without coagulation in the presence of the cationicemulsifier. Typically, the acrylic latex polymer has an electricallyneutral or cationic character prior to being combined with the aromaticrecycling agent and emulsifier.

The present invention provides a concentrated emulsion of an aromaticrecycling agent for use in the surface treatment composition. Theconcentrated emulsion preferably includes 50-80% aromatic recyclingagent, greater than 0 to 4% emulsifier and 16% to less than 50% water.The water typically further contains an acid buffer such as hydrochloricor phosphoric acid to provide an acidic pH (e.g. less than 3). Theconcentrated emulsion of an aromatic recycling agent is then combinedwith water, latex polymer and additional emulsifier to produce thesurface treatment composition of the invention that is applied to thesurface.

In an alternative embodiment of the invention, the concentrated surfacetreatment emulsion can include 25-40% recycling agent, 25-40% latexpolymer, greater than 0% to 6% emulsifier, and 14% to less than 50%water. The water typically further contains an acid buffer such ashydrochloric or phosphoric acid to provide an acidic pH (e.g. less than3). In this embodiment, additional water can be added to produce thesurface treatment composition of the invention that is applied to thesurface.

Moreover, the present invention provides a surface comprising a baseconcrete layer; a cured polymer-based layer comprising a latex polymer,an aromatic recycling agent and a cationic emulsifier on top of at leasta substantial portion of said base layer; a surface treatment layercomprising asphalt on top of said polymer-based layer; and aninterfacial layer between said cured polymer-based layer and saidsurface treatment layer and comprising a blend of said curedpolymer-based layer and said surface treatment layer. In accordance withthis embodiment, the surface treatment layer comprises a microsurfacingor a slurry seal layer.

In a preferred embodiment of the invention, the latex polymer includesan acrylic latex polymer derived from one or more of acrylic andmethacrylic polymers. For example, the latex polymer can include astyrene-acrylic latex polymer or a straight acrylic latex polymer. Thestyrene content is preferably from 0% to 65%, most preferably from 15 to25% by weight. In some embodiments, the latex polymer used to form theemulsion is an essentially electrically neutral emulsion prior to beingcombined with the emulsifier and aromatic recycling agent. The aromaticrecycling agent preferably has a low viscosity and can be, for example,RA-1.

The emulsifier in the emulsion is preferably a cationic emulsifier andmore preferably includes a cationic rapid set (CRS) emulsifier.Advantageously, the emulsion comprising a latex polymer and a smallamount of CRS emulsifier quickly penetrates into hairline cracks in agedconcrete or asphalt concrete and provides an air and water-tight sealover the surface. Also, the cationic charge of the emulsion allows theemulsion to better adhere to the negatively charged aged asphaltconcrete to which the emulsion is applied. It was surprising andunexpected that when depositing a surface asphalt concrete layer on topof the surface wetted by the emulsion, the cure time for the surfaceasphalt concrete layer would be reduced. Though not wishing to be boundby theory, it is believed that after the surface layer is applied, theemulsifier acts as an accelerator in the surface layer to promote quickcohesion development and strong adhesion to the aged surface.

These and other features and advantages of the present invention willbecome more readily apparent to those skilled in the art uponconsideration of the following detailed description, which describesboth the preferred and alternative embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafterwherein some, but not all embodiments, of the invention are described.Indeed, the invention can be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather,these embodiments are provided so that this disclosure will satisfyapplicable legal requirements. Although specific terms are employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation. The term “comprising” and variations thereofas used herein is used synonymously with the term “including” andvariations thereof and are open, non-limiting terms. As used in thespecification, and in the appended claims, the singular forms “a”, “an”,“the”, include plural referents unless the context clearly dictatesotherwise.

The method of restoring or treating a surface comprises applying anemulsion to wet the surface and depositing a surface treatment layer onthe surface while the surface remains wetted with the emulsion. Theemulsion can be applied to the surface to produce an emulsion layer thatcovers at least a substantial portion of the surface. The emulsion ofthe invention can also be used to seal a surface. The emulsion compriseswater, a latex polymer, an emulsifier and typically an aromaticrecycling agent. The surface to be treated, restored or sealed istypically an asphalt concrete surface that has undergone some degree ofoxidation of the asphalt; however, the surface can be other types ofsurfaces, such as cement concrete, unoxidized asphalt concrete, or anyother porous surface to which a surface asphalt concrete layer can beapplied.

Emulsion

The emulsion according to the invention is preferably an aqueousemulsion comprising water, latex polymer, a cationic emulsifier, and anaromatic recycling agent. In the aqueous emulsion, water is the carrierfor the other components in the emulsion. Preferably, solvents otherthan water are not used in the emulsion.

The emulsifier used in the emulsion according to the inventionpreferably includes a cationic emulsifier although a portion or all ofthe emulsifier used in the emulsion can include nonionic or amphotericsurfactants such as those described herein. In paving applications,asphalt emulsions are classified in ASTM D977 and D2397 by the time ittakes for “set” or curing into categories into three categories: rapidsetting (RS), medium setting (MS) or slow setting (SS). Before anemulsion can set, the emulsion is broken to separate the water from theparticles. The breaking time is determined by the stability of theemulsion, and the more stable the emulsion, the longer the breakingtime. The emulsifiers can also be classified based on the surface chargeas cationic, anionic, nonionic, and amphoteric. By combining surfacecharge characteristic with the setting time, emulsifiers used for pavingapplications can be classified as, for example, cationic rapid setting(CRS), cationic medium setting (CMS), and cationic slow setting (CSS),and these classifications are known in the art and can be readilymeasured in an emulsion as set forth in ASTM D977 and D2397. Cationicquick setting (CQS) emulsifiers fall somewhere between CRS and CMSemulsifiers in the set rate.

Because of their rapid set times, the preferred emulsifiers according tothe invention include the CRS emulsifiers. Examples of cationicemulsifiers classified as CRS emulsifiers that can be used in theinvention include REDICOTE® 4819, REDICOTE® E-64R, REDICOTE® E16,REDICOTE® E-9, REDICOTE® EM-44, REDICOTE® C-346, all from Akzo NobelSurface Chemistry and INDULIN® DF-80, INDULIN® DF-60, INDULIN® DF-40,INDULIN® DF-42, INDULIN® DF-30, INDULIN® R-20, AROSURF® AA-54, AROSURF®AA-78, AROSURF® AA-86 AND AROSURF® AA-89 from MeadWestvaco Corporation.However, CMS, CQS and CSS emulsifiers can also be used according to theinvention.

The amount of emulsifier in the emulsion is preferably sufficient toboth maintain a stable emulsion and adequately wet the surface to whichit is applied. This concentration can vary based the type of emulsifierused and on the other components of the emulsion, but is generally fromgreater than 0 to 2% by weight of the emulsion and more preferably from0.1% to 0.5% by weight of the emulsion. As discussed above, thepreferred emulsifier is a cationic emulsifier although the emulsifiercan include nonionic and/or amphoteric surfactants. For example, theemulsion can include a small amount of a nonionic or amphotericsurfactant (less than 0.3% by weight of the emulsion, and morepreferably less than 0.1% by weight of the emulsion) as part of thetotal emulsifier concentration.

The emulsion according to the invention comprises a latex polymer,preferably an acrylic latex polymer. The latex polymer, prior to theaddition of the emulsifier used in the emulsion applied to the surface,can be a cationic polymer dispersion, an essentially electricallyneutral polymer dispersion, or a combination thereof. Essentiallyelectrically neutral polymer dispersions can include those described inpending U.S. application Ser. Nos. 11/399,816; 11/399,817 and11/400,623, filed Apr. 7, 2006 and which are hereby incorporated byreference in their entirety. Methods of preparing the essentiallyelectrically neutral emulsions are described in more detail hereinbelow.

The acrylic latex polymer used in the invention is derived from one ormore of acrylic and methacrylic monomers. The acrylic latex polymer canbe a straight acrylic polymer or a styrene acrylic polymer and ispreferably a styrene-acrylic polymer. The total (meth)acrylic and(meth)acrylate (i.e. acrylic) content is from 35% to 100%, morepreferably 45-90%, and most preferably 65-85% by weight. The styrenecontent of the acrylic latex is preferably from 0% to 65%, morepreferably 5-50% or 10-30%, and most preferably 15-25% by weight. Thepolymer can be derived from up to 10% by weight of other monomers suchas acrylonitrile and acrylamide. The latex polymer preferably has aglass transition temperature, T_(g), of below 40° C., and morepreferably below 20° C. It has been found that the acrylic latexpolymers of the invention advantageously are not tacky when applied andcured and thus are less likely to adhere to machinery used to apply thesurface treatment layer than conventional latex polymers (e.g. SBR latexpolymers) used in paving applications. The emulsion according to theinvention preferably comprises 2 to 15% by weight latex polymer, morepreferably 3 to 10% by weight latex polymer, most preferably 4 to 7% byweight latex polymer (e.g. 5% by weight latex polymer).

The recycling agent of the emulsifier according to the invention caninclude any known recycling agent appropriate for the type of asphaltsurface that the emulsion is applied to. Recycling agents are classifiedinto types such as RA-1, RA-5, RA-25, and RA-75 as defined by ASTMD4552. The recycling agent used according to the invention is preferablymaterial that resembles the maltene fraction of asphalt such as a RA-1recycling agent, a RA-5 recycling agent, or mixtures thereof. Morepreferably, the recycling agent is a RA-i recycling agent such as thoseavailable as RA-1 from vendors such as San Joaquin Refining or TricorRefining or under the trade name HYDROLENE® (such as HYDROLENE® HT100T)from Sunoco.

Though not wishing to be bound by theory, it is believed that therecycling agent in the emulsion penetrates the surface it is applied toand replenishes the oily component that degrades over time in an asphaltsurface. Preferably, the recycling agent as used in the emulsion is highin aromatics and polar materials. The amount of recycling agent in theemulsion can be adjusted depending on the condition of the surface wherethe emulsion will be applied. If the surface is highly oxidized agedasphalt concrete, the amount of recycling agent can be increased toensure adequate dosing of the aged asphalt concrete with the recyclingagent. Alternately, if the surface is not asphalt concrete or has littleto no oxidation of the asphalt, the recycling agent can be reduced oromitted altogether from the emulsion formulation.

Preferably, the amount of aromatic recycling agent is from 0 or greaterthan 0 to 15% by weight, more preferably from 2 to 15% or 2 to 8% byweight, and most preferably from 3% to 6% by weight (e.g. 5% by weight).The ratio of the aromatic recycling agent to the latex polymer ispreferably from 1:10 to 5:1, more preferably from 1:3 to 3:1, 1:2 to2:1, or about 1:1.

Preferably, the composition of the invention does not include or issubstantially free of (includes less than 0.1% by weight) asphalt.However, although not preferred, a small portion (up to 10% by weight)of the recycling agent can be replaced by asphalt and the asphalt can bepresent in the emulsion in an amount of less than 0.5% by weight.

The emulsion can optionally further include other components in smallamounts. For example, the emulsion can include oxidation reducers thatimpart further beneficial properties to the surface to which theemulsion is applied. An example of an oxidation reducer is carbon black,which darkens the surface and prevents further oxidation. Theseadditional components are included in an amount from 0 to about 2% byweight.

The balance of the composition includes water in an amount of from 70%to 96% by weight, more preferably 80%-90% by weight.

The pH of the emulsion as applied is preferably from 1 to 4,particularly when the preferred cationic emulsifiers described hereinare used. Nevertheless, a higher pH can be used depending on the type ofemulsifier(s) included in the emulsion. For pH's of 1 to 4, the watertypically further contains an acid buffer such as hydrochloric orphosphoric acid to provide the acidic pH.

Production of the Electrically Neutral Polymer Dispersion

In one preferred embodiment, an essentially electrically neutral polymerdispersion can be used in the emulsion. The essentially electricallyneutral polymer dispersion has a surface charge that is approximately(essentially) electrically neutral and can be prepared using adispersion, mini-emulsion, or emulsion polymerization process, andpreferably an emulsion polymerization process is used. The emulsionpolymerization process can be continuous, batch, or semi-batch and ispreferably a semi-batch process. The process for preparing theessentially electrically neutral polymer dispersion can use a singlereactor or a series of reactors as would be readily understood by thoseskilled in the art. For example, a review of heterophase polymerizationtechniques is provided in M. Antonelli and K. Tauer, Macromol. Chem.Phys. 2003, vol. 204, p 207-219.

The essentially electrically neutral polymer dispersion is preferablyprepared by first charging a reactor with a seed latex, water, andoptionally at least one nonionic surfactant and/or at least one of themonomers. The seed latex helps initiate polymerization and helps producea polymer having a consistent particle size. Any seed latex appropriatefor the specific monomer reaction can be used and preferably apolystyrene seed is used. The initial charge typically also includes achelating or complexing agent such as ethylenediamine tetraacetic acid(EDTA). Other compounds such as buffers can be added to the reactor toprovide the desired pH for the emulsion polymerization reaction. Forexample, bases or basic salts such as KOH or tetrasodium pyrophosphatecan be used to increase the pH whereas acids or acidic salts can be usedto decrease the pH. The initial charge can then be heated to atemperature at or near the reaction temperature, for example, to between50° C. and 100° C. Preferably, the initial charge is heated to atemperature between 70° C. and 95° C.

After the initial charge, the monomers that are to be used in thepolymerization can be continuously fed to the reactor in one or moremonomer feed streams. The monomers are preferably supplied as apre-emulsion in an aqueous medium. Typically, an initiator feed streamis also continuously added to the reactor at the time the monomer feedstream is added although it may also be desirable to include at least aportion of the initiator solution to the reactor prior to adding amonomer pre-emulsion if a pre-emulsion is used in the process. Themonomer and initiator feed streams are typically continuously added tothe reactor over a predetermined period of time (e.g. 1.5-5 hours) tocause polymerization of the monomers and to thereby produce the polymerdispersion. The nonionic surfactant according to the invention and anyother surfactants are also typically added at this time as part ofeither the monomer stream or the initiator feed stream although they canbe provided in a separate feed stream. Furthermore, one or more bufferscan be included in either the monomer or initiator feed streams orprovided in a separate feed stream to modify or maintain the pH of thereactor.

As mentioned above, the monomer feed stream can include one or moremonomers. The monomers can be fed in one or more feed streams with eachstream including one or more of the monomers being used in thepolymerization process. It can also be advantageous to delay the feed ofcertain monomers to provide certain polymer properties or to provide alayered structure (e.g. a core/shell structure). In accordance with theinvention, one monomer can be provided in the polymerization process toproduce a homopolymer although typically two or more monomers arecopolymerized to produce a copolymer.

The monomers for use in the electrically neutral polymer dispersion arepreferably nonionic monomers. Exemplary nonionic monomers includestyrene, C1-C10 alkyl and C2-C10 hydroxyalkyl esters of acrylic andmethacrylic acid (e.g. ethyl acrylate, ethyl methacrylate, methylmethacrylate, 2-ethylhexyl acrylate, butyl acrylate, butyl methacrylate,hydroxypropyl acrylate, hydroxypropyl methacrylate,dimethylhydroxypropyl (meth)acrylate, 2-hydroxyethyl acrylate,hydroxyethyl methacrylate, 2-hydroxybutyl methacrylate and2-propylheptyl (meth)acrylate), 2-acetoacetoxyethyl methacrylate (AAEM),1,4-butanediyl diacrylate, acrylamide, methacrylamide,N-methylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide,N-isopropylacrylamide, N-t-butylacrylamide, N-methylolacrylamide,N-vinylformamide, N-vinylmethylacetamide, vinyl esters (e.g. vinylacetate, vinyl propionate, vinyl butyrate, and vinyl caprolate),divinylbenzene, vinyltriethoxysilane, t-butylstyrene, isopropylstyrene,p-chlorostyrene, acrylonitrile, methacrylonitrile, C4-C8 dienes (e.g.butadiene), isoprene, vinyl chloride, vinylidene chloride, and the like,and mixtures thereof. The monomers used according to the invention caninclude cross-linking monomers, such as butadiene, 1,4-butanediyldiacrylate, and divinylbenzene.

The monomers for use in the electrically neutral polymer dispersion canalso include a small amount (0.5% by weight or less, based on the totalmonomer weight) of one or more ionic monomers. Exemplary ionic monomersinclude carboxylic acid monomers (e.g., itaconic acid, fumaric acid,acrylic acid, and methacrylic acid).

In one preferred method for producing an essentially electricallyneutral polymer dispersion, the monomers include styrene and at leastone monomer selected from the group consisting of (meth)acrylatemonomers, to produce a styrene-acrylic latex. More preferably, themeth(acrylate) monomers include one or more monomers selected from thegroup consisting of 2-ethylhexylacrylate, n-butylacrylate, and methylmethacrylate. In another preferred embodiment of the invention, astraight acrylic polymer can be produced using (meth)acrylate monomerssuch as the acrylate and methacrylate monomers listed above. For boththe styrene acrylic and straight acrylic polymer dispersions, themonomers also preferably include acrylamide, methacrylamide andderivatives thereof (e.g. N-methylacrylamide, N,N-dimethylacrylamide,N,N-diethylacrylamide, N-isopropylacrylamide, N-t-butylacrylamide, andN-methylolacrylamide) to increase the stability of the dispersion.

The molecular weight of the polymers in the electrically neutral polymerdispersion produced by the process described above can be adjusted byadding a small amount of molecular weight regulators, generally up to 2%by weight, based on the monomers being polymerized. Particularregulators which can be used are organic thio compounds, preferablytert-dodecylmercaptan, and also allyl alcohols and aldehydes.

The initiator feed stream used in accordance with the invention caninclude at least one initiator or initiator system that is used to causethe polymerization of the monomers in the monomer feed stream. Theinitiator stream can also include water and other desired componentsappropriate for the monomer reaction to be initiated. The initiator canbe any initiator known in the art for use in emulsion polymerizationsuch as azo initiators; ammonium, potassium or sodium persulfate; or aredox system that typically includes an oxidant and a reducing agent.Commonly used redox initiation systems are described e.g., by A. S.Sarac in Progress in Polymer Science 24(1999), 1149-1204. Preferredinitiators include azo initiators and aqueous solutions of sodiumpersulfate. The initiator stream can optionally include one or morebuffers or pH regulators, such as those described above.

In addition to the monomers and initiator, a nonionic surfactant is fedto the reactor. The nonionic surfactant can be provided in the initialcharge of the reactor, provided in the monomer feed stream, provided inan aqueous feed stream, provided in a pre-emulsion, provided in theinitiator stream, or a combination thereof. The nonionic surfactant canalso be provided as a separate continuous stream to the reactor. Thenonionic surfactant is typically provided in an amount of 1-5% by weightin the electrically neutral polymer dispersion, based on the totalweight of monomer and surfactant, and is preferably provided in anamount less than 2% by weight in the electrically neutral polymerdispersion.

The preferred nonionic surfactant in producing the essentiallyelectrically neutral polymer dispersion comprises an alkylene oxideadduct such as an ethylene oxide (EO)_(m), propylene oxide (PO)_(n)and/or butylene oxide (BO)_(p) adduct of an alkyl, alkylbenzene ordialkylbenzene alcohol wherein 0<(m+n+p)≦14, preferably 0<(m+n+p)≦12,and more preferably 0<(m+n+p)≦10 (e.g. 6<(m+n+p)≦10). The nonionicsurfactant can comprise an ethylene oxide adduct of an alcohol (with n=0and p=0), a propylene oxide adduct of an alcohol (with m=0 and p=0), abutylene oxide adduct of an alcohol (with m=0 and n=0), or an adduct ofan alcohol with a combination of two or more of ethylene oxide,propylene oxide and butylene oxide (with two or more of m, n and p beinggreater than 0). In the event that two or more of m, n and p are greaterthan 0, the ethylene oxide, propylene oxide and/or butylene oxide can beprovided as a random or block copolymer. More preferably, the nonionicsurfactant is an ethylene oxide adduct of an alkyl alcohol, with n=0 andp=0. The alkyl alcohol is preferably a branched or straight chainhydrocarbon having a single hydroxyl group, preferably a terminalhydroxyl group, that is ethoxylated. The alkyl group preferably includes10 to 22 carbon atoms and more preferably 10 to 16 carbon atoms.Particularly preferred nonionic emulsifiers are ethylene oxide (EO)_(m)adducts of tridecyl alcohol, wherein m=6, 8, or 10, such as thoseavailable from BASF under the LUTENSOL™ trademark. The term “nonionic”as used herein refers to materials that do not dissociate in thedispersion into positively and negatively charged species.

The nonionic surfactant for producing the essentially electricallyneutral polymer dispersion preferably has a cloud point temperaturebelow the polymerization temperature used to produce the polymerdispersion when the polymerization is in an aqueous solution. The cloudpoint temperature, also known as a cloud point, cloud temperature, orsolubility inversion temperature, is the temperature at which thenonionic surfactant solution becomes cloudy (i.e. at and above thattemperature the solution appears cloudy or turbid). As used herein, thecloud point temperature refers to the cloud point of a 1% aqueoussolution of the surfactant. The cloud point temperature can bedetermined by visual observation of the solution over a range oftemperatures, or by light scattering measurements. As used herein, thecloud point temperature is determined using ASTM D-2024-65R03.Preferably, the cloud point temperature for a 1% aqueous solution of thenonionic surfactant is between 30° C. and 90° C., more preferablybetween 35° C. and 85° C. For the preferred ethylene oxide (EO)_(m)adducts of tridecyl alcohol, wherein m=6, 8, or 10, the cloud pointtemperatures are 38-43° C., 40-45° C., and 73-82° C., respectively. Thenonionic surfactant also preferably has a HLB (hydrophilic lipophilicbalance) at room temperature such that 8<HLB<15. More preferably, theHLB is 14 or less.

In addition to the nonionic surfactant described above, it may also bedesirable to include an additional nonionic surfactant. Suitablenonionic surfactants include polyoxyalkylene alkyl ethers andpolyoxyalkylene alkylphenyl ethers (e.g. diethylene glycol monoethylether, diethylene glycol diethyl ether, polyoxyethylene lauryl ether,polyoxyethylene stearyl ether, and polyoxyethylene nonylphenyl ether);oxyethylene-oxypropylene block copolymers; sorbitan fatty acid esters(e.g. sorbitan monolaurate available as SPAN® 20 from Merck SchuchardtOHG, sorbitan monooleate available as SPAN® 80 from Merck SchuchardtOHG, and sorbitan trioleate available as SPAN® 85 from Merck SchuchardtOHG); polyoxyethylene sorbitan fatty acid esters (e.g. polyoxyethylenesorbitan monolaurate available as TWEEN® 20 and TWEEN® 21 from Uniqema,polyoxyethylene sorbitan monopalmitate available as TWEEN® 40 fromUniqema, polyoxyethylene sorbitan monstearate available as TWEEN® 60,TWEEN® 60K, and TWEEN® 61 from Uniqema, polyoxyethylene sorbitanmonooleate available as TWEEN® 80, TWEEN® 80K, and TWEEN® 81 fromUniqema, and polyoxyethylene sorbitan trioleate available as TWEEN® 85from Uniqema); polyoxyethylene sorbitol fatty acid esters (e.g.tetraoleic acid polyoxyethylene sorbitol); glycerin fatty acid esters(e.g. glycerol monooleate); polyoxyethylene glycerin fatty acid esters(e.g. monostearic acid polyoxyethylene glycerin and monooleic acidpolyoxyethylene glycerin); polyoxyethylene fatty acid esters (e.g.polyethylene glycol monolaurate and polyethylene glycol monooleate);polyoxyethylene alkylamine; and acetylene glycols.

It may also be desirable to include one or more amphoteric surfactantsin the polymerization step. Suitable amphoteric surfactants includethose described in U.S. Pat. No. 6,540,822, which is herein incorporatedby reference. An exemplary amphoteric surfactant is REDICOTE® E-7000,which is available from Akzo Nobel.

Although additional nonionic or amphoteric surfactants can be combinedwith the nonionic surfactant of the invention, an anionic surfactant istypically not included in the emulsion polymerization reaction.Furthermore, a cationic surfactant is typically not used in producingthe essentially electrically neutral polymer dispersion. However,because a cationic emulsifier will be added to the polymer dispersionbefore application to the asphalt concrete surface, additional cationicsurfactants can be added in the polymerization step or at another stepin the process.

Once polymerization is completed, the essentially electrically neutralpolymer dispersion is preferably chemically stripped thereby decreasingits residual monomer content. This stripping process can include achemical stripping step and/or a physical stripping step. Preferably,the polymer dispersion is chemically stripped by continuously adding anoxidant such as a peroxide (e.g. t-butylhydroperoxide) and a reducingagent (e.g. sodium acetone bisulfite), or another redox pair to thereactor at an elevated temperature and for a predetermined period oftime (e.g. 0.5 hours). Suitable redox pairs are described by A. S. Saracin Progress in Polymer Science 24, 1149-1204 (1999). An optionaldefoamer can also be added if needed prior to or during the strippingstep. In a physical stripping step, a water or steam flush is used tofurther eliminate the non-polymerized monomers in the dispersion. Oncethe stripping step is completed, the pH of the polymer dispersion can beadjusted and a biocide or other additives can be added. Cationic and/oramphoteric surfactants can optionally be added after the stripping stepor at a later time if desired. The polymer particles of the resultantpolymer dispersion preferably have an average particle size from 100 to500 nm, more preferably 130-250 nm. The polymer particles preparedaccording to the invention are characterized by having a narrow particlesize distribution. Specifically, the resultant volume-averagedistribution of polymer particles in the polymer dispersion preferablyhas a standard deviation of less than 30%.

Once the polymerization reaction is complete, and the stripping step iscompleted, the temperature of the reactor is reduced, thus making thenonionic surfactant water-soluble. While not wishing to be bound bytheory, it is believed that the hydrocarbon chain of the nonionicsurfactant immobilizes the surfactant into the monomer swollenparticles, and the surfactant becomes physically trapped in the polymerchain. On the other hand, it is believed that the hydrophilic (EO)_(m)and/or (PO)_(n) chain remains at the polymer particle/water interfaceand extends towards the water phase, providing colloidal stability forthe polymer dispersion. Therefore, though the polymerization temperatureis below the cloud point temperature of the nonionic surfactant, thesurfactant molecules do not migrate to the water phase. Thus, becausethere are limited amounts of free nonionic surfactant in the water phaseof the latex, it is believed that the mechanical properties of the driedfilm are not adversely affected by the presence of the nonionicsurfactants.

The polymer dispersion following the polymerization step as outlinedabove is essentially electrically neutral in that there are eitheressentially no charged groups in the polymer or there is essentially abalance of anionic and cationic charged groups in the polymer. Theelectrophoretic mobility (μ) of the polymer dispersion can be used tomeasure the zeta potential to show the charge of the polymer dispersionalthough it is noted that the measurement may indicate an anioniccharacter even though the polymer dispersion is essentially electricalneutral. For example, the resulting polymer dispersion can have a lownegative surface charge due to the presence of grafted sulfate groupswhen a persulfate initiator is used or due to water molecules beingabsorbed to the polymer surface. However, the polymer dispersion wouldbe classified as an essentially electrically neutral polymer dispersionas it is neutral and non-ionic in terms of the dispersion stability andacts with a nonionic character upon addition of anionic or cationicsurfactants, electrolytes, or high valency electrolytes. Examples ofdispersions that are essentially electrically neutral in terms ofdispersion stability and act with a nonionic character, but have ioniczeta potential measurements are provided in S. Usui, Y. Imamura and E.Barouch, Destabilization of oil-in-water emulsion with inorganicelectrolytes in the absence and in the presence of sodium dodecylsulfate, J. Dispersion Science and Technology 8(4), 359-384 (1987)(measured zeta potential of decane particles as a function ofelectrolyte concentration show strongly negatively charged even withoutthe anionic surfactant) and S. Usui and H. Sasaki, Zeta potentialmeasurements of bubbles in aqueous surfactant solutions, J. Colloid andInterface Science, 65(1), 36-45 (1978) (zeta potential of argon gasbubbles in the presence of nonionic surfactant C₁₂POE measures highlynegative).

Because of the absence of anionically charged surfactants and vinylacids, the polymer dispersions of the invention are colloidally stableat a wide range of pH's, can include no or low levels of electrolytes,and are stable (do not coagulate) in the presence of the cationicemulsifier. Moreover, the electrically neutral polymer dispersions ofthe invention have a low electrical conductance and a high electricalresistance as is desirable as an additive to cement or application toasphalt to act as a moisture barrier.

Preparation and Application of the Emulsion

The emulsion applied according to the invention includes water, at leastone polymer latex, a cationic emulsifier, and for asphalt applications arecycling agent. These ingredients can be combined in any order to forma stable emulsion. Preferably, a concentrated emulsion is providedincluding the recycling agent and that emulsion is shipped or stored andthe sprayable emulsion is prepared from the concentrated emulsion.

In one preferred embodiment, a base emulsion comprising water, therecycling agent, and a nonionic, cationic or amphoteric surfactant isfirst prepared. The concentrated emulsion preferably includes 50-80% andmore preferably 60-75% by weight aromatic recycling agent, greater than0 to 4% and more preferably 0.1 to 1.5% by weight emulsifier, and 16% toless than 50% and more preferably 24 to 40% by weight water. The watertypically further contains an acid buffer such as hydrochloric orphosphoric acid to provide an acidic pH (e.g. less than 3). Theconcentrated emulsion of an aromatic recycling agent is then combinedwith water, latex polymer and additional emulsifier to produce thesurface treatment composition of the invention. For example, an aqueouscationic emulsifier solution can be mixed with the base emulsion, whichdilutes the base emulsion. A latex emulsion such as a cationic or anelectrically neutral latex emulsion can then be added to the dilutedbase emulsion, typically in a ratio of latex emulsion to diluted baseemulsion of from 1:5 to 1:20, preferably about 1:10. The pH can beadjusted at each step with hydrochloric or phosphoric acid. Thepreferred pH of the emulsion to be applied to the surface is from about1 to about 4. The resulting emulsion includes amounts of the water,latex polymer, recycling agent and emulsifier consistent with the valuesdiscussed herein.

In an alternative embodiment of the invention, a concentrated surfacetreatment emulsion that includes 25-40% more preferably 30-38% by weightrecycling agent, 25-40% and more preferably 30-38% by weight latexpolymer, greater than 0% to 6% and more preferably 1.0-2.5% by weightemulsifier, and 14% to less than 50% and more preferably 22-39% byweight water. For example, the composition could include 35% aromaticrecycling agent, 35% latex polymer, 2% emulsifier and 28% water. Thewater typically further contains an acid buffer such as hydrochloric orphosphoric acid to provide an acidic pH (e.g. less than 3). In thisembodiment, additional water and optionally additional acid buffer canbe added to produce the surface treatment composition of the inventionthat is applied to the surface.

The emulsion is applied to a surface to be treated, restored or sealedaccording to the invention. Prior to application of the emulsion, thesurface to be treated is usually cleaned to remove excess surface dirt,weeds, and contaminants by, for example, brushing the surface, blastingthe surface with compressed air, or washing the surface.

The emulsion can be applied using any suitable method for applying aliquid to a porous surface, such as brushing, wiping and drawing, orspraying. Spraying is the preferred method of application of theemulsion because a very thin layer of the emulsion can be applied in ashort period of time. The emulsion is preferably applied at atemperature between 60° F. and 150° F. The emulsion also has a viscosityat the application temperature that allows it to be sprayed upon thesurface and preferably has a viscosity of from 1 to 5 centipoise. Theemulsion of the invention is preferably applied in an amount of0.01-0.10 gal/yd² to the surface. Because of the low application rateand viscosity of the emulsion, the emulsion forms a very thin emulsionlayer on the aged concrete surface and provides substantially no bindingstrength to the aged concrete surface, even when it is fully cured. Forexample, to the extent the resulting emulsion layer has any thickness atall, the emulsion layer has a thickness of 2 mm or less.

The emulsion once applied wets the surface thereby forming an emulsionlayer on at least a portion and typically at least a substantial portion(e.g. more than 50%) of the surface. When the emulsion is applied to theaged concrete surface, water loss occurs in the emulsion, primarily dueto adsorption of the water to the old pavement surface. The water alsodelivers the emulsifier, aromatic recycling agent and latex polymer tothe aged concrete surface. Preferably, the emulsion penetrates andadheres to the surface it is applied to, cures in a reasonably rapidtime, and provides a water-tight and air-tight barrier on the oldersurface. The emulsion layer also promotes adhesion between the oldersurface and the later applied surface treatment layer. It is desirablefor the emulsion to be easily applied and have an adequate shelf life.

With a traditional slurry seal or microsurfacing operation, the surfaceto which the slurry seal or microsurfacing layer is to be applied issprayed with water to prewet the surface. The paving machines used formicrosurfacing and slurry seal ordinarily have water tanks and sprayingequipment already mounted. These spraying systems can be used for theemulsion instead of being used just for water. Therefore, the emulsioncan be applied to the surface immediately prior to application of thesurface layer in a single operation. Thus, both the time for applicationand time for curing, as well as the costs associated with preventivemaintenance operations, are reduced.

Typically, the paving machines used for the slurry seal andmicrosurfacing operations have limited space to store materials.Accordingly, a concentrated emulsion comprising the recycling agent istypically produced at an asphalt emulsion plant and then transported tothe job site and loaded to a tank associated with the paving machine.This concentrated emulsion can then be diluted with water and anyadditional components (e.g. cationic emulsifier, polymer latex, and acidbuffer) can be added to the paving machine for application to thesurface to the treated.

The emulsion penetrates visible and microscopic cracks of the agedsurface. Though the surface layer is applied while the aged surface iswetted with the emulsion, the water evaporates from the emulsion afterapplication of the surface layer to form a continuous polymer film overthe aged surface and in the cracks of the surface. This film over theaged surface provides a seal which is both water tight and air tight,absorbs stress, adheres strongly to the aged pavement, and prevents orreduces formation of reflective cracks in the new surface layer.

Application of the Surface Layer

After the aged surface is wetted with the emulsion as described above,the surface layer of asphalt concrete is deposited onto the wetted agedsurface using a cold paving technique such as microsurfacing or slurryseal. The composition of the surface layer mixture includes asphaltmixtures used for microsurfacing, slurry seal, or cold mix paving. Thesurface treatment layer as applied includes asphalt (bitumen), water, anemulsifier, aggregate, optional polymer modifiers, and optionaladditives.

The specifications for classifying the aggregate for use inmicrosurfacing and slurry seal applications have been developed by theInternational Slurry Surfacing Association in “Recommended PerformanceGuidelines for Emulsified Asphalt Slurry Seal,” A105 (Revised), June2004 and “Recommended Performance Guidelines for Micro-Surfacing,” A143(Revised), June 2004 and by the Federal Highway Administration in“Surface Rehabilitation Techniques: State of the Practice Design,Construction, and Performance of Microsurfacing,” Hassan Raza, FederalHighway Administration, FHWA-SA-94-051. For microsurfacing applications,the aggregate can be an ISSA Type II or III aggregate. For slurry sealapplications, the aggregate can be an ISSA Type I, II or III aggregate.Suitable aggregates for use in the invention include Delta aggregate andTranspcos aggregate (ISSA Type II aggregates commercially available fromCapitol Aggregates) and Blue Circle aggregate (an ISSA Type II aggregatecommercially available from Blue Circle). The aggregate is typicallywetted with from about 4 to about 16 parts by weight water, morepreferably, from about 8 to about 15 parts by weight water, prior tobeing combined with the other components of the formulation. The amountof water added is typically dependent on the fines content and theiractivity in the aggregate.

In a preferred embodiment, gap-graded aggregate is used in the surfacelayer mixture. Gap-graded aggregate allows for faster evaporation ofwater from the surface seal which decreases the amount of time forcuring the surface layer. Because of the larger aggregate used, thesurface layer has more void space than if a single modal aggregate isused. The resulting cured surface layer provides excellent skidresistance on the driving surface because rainwater drains quicklythrough the voids within the surface layer. A surface layer with a highdegree of voids (for example, through the use of gap-graded aggregate)also reduces the traffic noise.

The surface layer formulation of the invention includes an asphalt(bitumen) emulsion, and the asphalt emulsion is preferably added to thesurface layer formulation in an amount from about 8 to about 25 parts byweight, and more preferably in an amount from about 10 to about 15 partsby weight. Suitable asphalt emulsions for the surface layer formulationinclude SS-1, SS-1h, CSS-1, CSS-1h, CQS-1h and QS emulsions,particularly for slurry seal formulations, and more preferably includean emulsion including a CQS or CMS emulsifier and a small amount of aCRS emulsifier. For microsurfacing applications, the asphalt emulsionfor the surface layer formulation preferably is a CSS-1h emulsion thathas been polymer-modified as discussed in more detail below and thatpreferably includes a small amount of a CRS emulsifier. Preferably, theasphalt emulsions for the surface layer formulation include betweenabout 30 and about 80 percent bitumen (asphalt), and more preferably,between about 65 and about 75 percent bitumen. The bitumen preferablyhas a mean particle diameter of about 1 to about 10 microns, morepreferably, about 2 to about 3 microns. The asphalt emulsionsconventionally used in cold paving applications have a pH in the rangeof 1.0 to 1.5 and are typically made with an asphalt having a high acidnumber. Typically, the pH of the asphalt emulsion is produced throughthe use of acids such as hydrochloric, phosphoric, sulfuric, acetic,formic and oxalic acids. It is well known in the art that asphaltemulsions having higher pH's have been known to either not developenough cohesion or to have slow cohesion development resulting inincreased curing time being needed before the newly paved surface can beopened to traffic. The asphalt emulsions used in accordance with theinvention can have a pH in the range of 1.0 to 1.5 but pH's in thisrange are not required and asphalt emulsions having a pH of greater than1.5, or even greater than 2.0 or 3.0, can be used in accordance with theinvention. In addition, the asphalt formulations can include asurfactant and suitable surfactants are conventional in the art.Preferably, the asphalt emulsion adheres to the standards of the ASTMD977, ASTM D2397, AASHTO M140 and AASHTO M208.

The asphalt emulsion for the surface treatment layer formulation istypically prepared by first preparing a soap solution containing waterand one or more surfactants, and then adjusting the pH of the soapsolution using an acid such as HCl as mentioned above. The soap solutionand preheated asphalt are then generally pumped into a colloid millwhere high shear mixing produces the asphalt emulsion having asphaltdroplets dispersed in the water.

Typically for microsurfacing formulations and optionally for slurry sealoperations, the asphalt emulsions are polymer modified, e.g., toincrease the strength and durability of the resulting asphalt-based,cold paving formulations and to decrease the curing times of theseformulations. Typically, a polymer latex is added to the soap solutionand the asphalt emulsion is produced as discussed above. Alternatively,the polymer latex can be added to the asphalt emulsion after it has beenprepared or the polymer latex can be combined with the asphalt prior tomixing the asphalt with the soap solution to produce the asphaltemulsion.

Suitable polymer lattices for the surface layer formulation for use inmicrosurfacing formulations include cationic SBR (styrene-butadienerubber) lattices, natural rubber lattices, and polychloroprene lattices(e.g. NEOPRENE® lattices available from E. I. Du Pont de Nemours). SBS(poly(styrene-butadiene-styrene)) block copolymers and EVA(ethylene-vinyl acetate) copolymers can also be used but typically mustbe added slowly to heated asphalt (e.g. 160-170° C.) and then subjectedto high shear mixing to disperse the polymer in the asphalt prior toforming the asphalt emulsion. Preferably, a cationic SBR latex is usedin the asphalt emulsion. The cationic SBR latex emulsion typicallyincludes between about 0.1 and about 10%, more preferably between about1.0% and about 4.0% by weight cationic surfactants. The SBR latexemulsion is typically included in the asphalt emulsion in an amount fromgreater than 0 to about 6%, more preferably from 3.0 to 3.5% by weight.Suitable cationic SBR latices for use in the invention include BUTONAL®NX1118, BUTONAL® NX 1138, and BUTONAL® NS 198, commercially availablefrom BASF Corporation.

The asphalt-based surface layer typically includes aggregate, water, andan asphalt emulsion. The asphalt-based surface layer typically alsoincludes Portland cement, lime, alum, and the like. Alternatively or inaddition, the asphalt-based surface layer can also include at least onefirst compound selected from the group consisting of alkali metal salts,ammonium salts, alkali metal hydroxides and ammonium hydroxide; and atleast one second compound preferably selected from the group consistingof Group IIA, Group IIIA, Group IIIB, copper, zinc, cadmium, manganese,iron, cobalt and nickel salts. Suitable first and second compounds aredisclosed in U.S. Pat. No. 6,855,754, which is incorporated by referenceherein in its entirety.

The result of the method of the invention is a multilayer surfacecomprising a base concrete layer; a cured polymer-based layer comprisinga latex polymer, an aromatic recycling agent and a emulsifier on top ofat least a substantial portion of said base layer; a surface treatmentlayer comprising asphalt on top of said polymer-based layer; and aninterfacial layer between said cured polymer-based layer and saidsurface treatment layer and comprising a blend of said curedpolymer-based layer and said surface treatment layer. The interstitiallayer forms in this manner because the emulsion layer is not fully curedwhen the surface treatment layer is applied and some mixing occurs onthe interface between these layers. The surface treatment layertypically comprises a microsurfacing or a slurry seal layer.

The electrically neutral lattices used in one embodiment of theinvention are further described in the following examples. The examplesare merely illustrative and do not in any way limit the scope of theinvention as described and claimed. All parts are parts by weight unlessotherwise noted.

EXAMPLE 1 Synthesis of an Electrically Neutral Acrylic Latex

The following ingredients were charged in a reaction vessel: 320.3 gwater, 14.3 g of a 32% active seed aqueous emulsion (polystyrene), 0.7 gof a 40% aqueous solution of ethylene diamine tetraacetic acid (EDTA),and 0.7 g. of a 10% aqueous solution of potassium hydroxide (KOH). Themixture was heated to 80° C. From an initiator feed of 17.8 g water and1.9 g sodium persulfate, 12% was removed and added to the reactionmixture. Two separate feeds were added to the vessel at a constant feedrate. The remainder of the initiator feed was added at a constant feedrate over 4.5 hours. A monomer emulsion feed, consisting of 543.1 gwater, 21.3 g of a 90% active nonionic surfactant composed of an 8-moleethylene oxide adduct of tridecyl alcohol, 5.8 g. of 10% aqueous KOH,27.2 g of 53% aqueous acrylamide, 96.0 g. styrene, and 849.6 g n-butylacrylate (n-BA), was added over 4.0 hours to the reactor. During theduration of the feeds, the temperature was maintained at 80° C. Afterthe feeds were completed, the monomer emulsion tank was flushed with28.8 g water. After a 30 minute post-reaction period the dispersion waspost-stripped by adding the following two mixtures as two separate feedsover the course of an hour at a constant temperature of 80° C.: (a) 2.6g 70% tert-butyl hydroperoxide solution and 24.0 g water, and (b) 2.0 gsodium metabisulfite, 1,2 g acetone, and 23.4 g water. After thetemperature was maintained for 15 minutes following the two additionalfeeds, the polymer dispersion was cooled, and optional post-additions(such as biocide) were added. The final product had 49.6% total solids,a mean particle size of 196 nm, a pH of 3.2, a viscosity of 400 cps, anda glass transition temperature (T_(g)) of −42° C.

EXAMPLE 2 Preparation of a Surface-Wetting Emulsion

An example emulsion was prepared according to the invention using thelatex described in Example 1 as the latex, RA-1 (Golden Bear OilSpecialties, Calif.) as the recycling agent, and Redicote® E-4819 (AkzoNobel) as the cationic rapid set emulsifier. A base RA-1 emulsion wasfirst prepared by preparing an aqueous solution of 1.6% LUTENSOL® TDA-8and adjusting the pH of the solution to about 2 with hydrochloric acid(HCl). RA-1 recycling agent was added to the adjusted solution andemulsified into the solution using a colloid mill. The resultant baseRA-1 emulsion had a RA-1 content of 69% by weight, a viscosity of 35mPa·s, and a pH of 2.3.

A CRS emulsifier solution of pH 1.5 was prepared using 0.12% REDICOTE®E-4819 in aqueous solution and HCl as a pH adjuster. The base RA-1emulsion was diluted to 5% RA-1 using the CRS emulsifier solution toform a diluted RA-1 emulsion. An electrically neutral polymer latexprepared in accordance with Example 3 above was added to the dilutedRA-1 emulsion in a weight ratio of approximately 1:10 such that theresulting surface wetting emulsion had a polymer content of 5% byweight.

EXAMPLE 3 Penetration of Emulsions into Asphalt Pavement

A patch of water (about 20 ml) was placed onto an aged asphalt pavementsurface and it was observed that the water penetrated the surface rightaway and disappeared after 2 min. As a control, a water patch similar insize was placed on a new asphalt pavement surface, and it was observedthat (1) after 2 min the water had not yet visibly started to penetratethe surface, (2) after 20 min about one third of the original size ofthe water patch had disappeared into the pavement, and (3) after 60 minthe water had disappeared (the surface was still wet).

EXAMPLE 4 Penetration of Surfactant Solutions

The following solutions were prepared: (1) 0.13% by weight of REDICOTE®E-4819 (CRS surfactant) in water; (2) 1.0% by weight of LUTENSOL® TDA-8in water. For each of the two solutions, separate patches (20 ml liquid)were placed on top of an aged asphalt pavement surface. A control patchof pure water was also added to the aged asphalt surfactant. It wasobserved that the pure water patch disappeared after 120 seconds,solution 1 disappeared after 50 seconds, and solution 2 after 20seconds.

EXAMPLE 5 Water Penetration on Top of Treated Aged Asphalt Surface

For this experiment, the following surface-wetting emulsions wereprepared: (1) 5% RA-1 emulsion in water, containing 1.0% LUTENSOL®TDA-8; (2) a surface-wetting emulsion like the one described in Example2 but using BUTONAL® NX 1118 as the polymer latex instead of theelectrically neutral polymer latex; (3) a surface-wetting emulsion asdescribed in Example 2. Emulsions 1-3 were sprayed onto a surface ofaged asphalt pavement, and it was observed that the treated surfacedeveloped a black color for all the cases. After placing a patch ofwater on top of the treated surfaces (5 ml water), it was observed thatthe water did not penetrate the surface, but it stayed on top until itevaporated. As a comparison, when water is placed on top of untreatedaged asphalt surface, it disappears into the pavement within 2 min (asdescribed above). Comparing treated surfaces (2) and (3), it wasobserved that (2) felt tacky to the touch, whereas (3) did not.Accordingly, emulsion (3) is preferred and it less likely to adhere tomachinery used to apply the surface treatment layer.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which thisinvention pertains having the benefit of the teachings presented in theforegoing description. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed andthat modifications and other embodiments are intended to be includedwithin the scope of the following appended claims.

1. A method of treating a surface, comprising: (a) applying an emulsionto the surface thereby wetting the surface, said emulsion comprising 70%by weight water or greater, a latex polymer, an aromatic recyclingagent, an emulsifier, and less than 0.5% by weight asphalt; and (b)depositing a surface treatment layer on the surface, wherein saiddepositing step occurs while the surface remains wetted by the emulsionin said applying step.
 2. The method as claimed in claim 1, wherein thelatex polymer includes a straight acrylic latex polymer, a styreneacrylic latex polymer, or a combination thereof.
 3. The method asclaimed in claim 1, wherein the surface is an asphalt concrete surface.4. The method as claimed in claim 1, wherein the surface treatment layeris a microsurfacing layer.
 5. The method as claimed in claim 1, whereinthe surface treatment layer is a slurry seal layer.
 6. The method asclaimed in claim 1, wherein the emulsifier includes a cationicemulsifier.
 7. The method as claimed in claim 6, wherein the emulsifierincludes a cationic rapid set emulsifier.
 8. The method as claimed inclaim 1, wherein the aromatic recycling agent includes RA-1.
 9. Themethod as claimed in claim 1, wherein said applying step comprisesspraying the emulsion onto the surface to wet the surface.
 10. Themethod as claimed in claim 1, further comprising the steps of: mixingthe aromatic recycling agent with water and an emulsifier to produce aconcentrated emulsion of the aromatic recycling agent; combining theemulsifier, water, and the latex polymer with the concentrated emulsionto produce the emulsion used in said applying step.
 11. The method asclaimed in claim 10, wherein the latex polymer is an electricallyneutral latex polymer.
 12. The method as claimed in claim 1, furthercomprising the steps of: preparing a concentrated emulsion by combiningwater, an aromatic recycling agent, a latex polymer and an emulsifier;and diluting the concentrated emulsion with water to produce theemulsion used in said applying step.
 13. The method as claimed in claim12, wherein the latex polymer is an electrically neutral latex polymer.14. The method as claimed in claim 1, wherein the emulsion in saidapplying step is substantially free of asphalt.
 15. The method asclaimed in claim 1, wherein the surface treatment layer comprisesasphalt.
 16. The method as claimed in claim 15, wherein the surfacetreatment further comprises aggregate.
 17. The method as claimed inclaim 16, wherein the surface treatment layer further comprises waterand an emulsifier.
 18. The method as claimed in claim 17, wherein thesurface treatment layer further comprises a polymer modifier.
 19. Themethod as claimed in claim 1, wherein the emulsion comprises 80% byweight water or greater.
 20. A method of treating a surface, comprising:(a) applying an emulsion to the surface thereby wetting the surface,said emulsion comprising 70% by weight water or greater, a latexpolymer, an aromatic recycling agent, an emulsifier, and less than 0.5%by weight asphalt; and (b) depositing a surface treatment layer on thesurface, the surface treatment layer comprising asphalt, water, anemulsifier, and aggregate, wherein said depositing step occurs while thesurface remains wetted by the emulsion in said applying step.
 21. Themethod as claimed in claim 20, wherein the emulsion in said applyingstep is substantially free of asphalt.
 22. The method as claimed inclaim 20, wherein the surface treatment layer further comprises apolymer modifier.
 23. The method as claimed in claim 20, wherein theemulsion comprises 80% by weight water or greater.
 24. The method asclaimed in claim 1, wherein the emulsion in said applying step does notinclude asphalt.
 25. The method as claimed in claim 20, wherein theemulsion in said applying step does not include asphalt.